Radio transmission arrangement



Sept. 17, 1940. A. wlEssNER 2,214,915

RADIO TRANSMISSION ARRANGEMENT Filed DSC. 16, 1937 Patented Sept. 17,1940 UNITED STATES PATENT OFFICE Alfred Wiessner, Berlin, Germany,assigner to C. Lorenz Aktiengesellschaft, Berlin-Tempelhof,

Germany, a company Application December 16, 1937, Serial No. 180,116 InGermany December 21, 1936 2 Claims.

The present invention relates to communication systems especiallyadapted for transmitting a plurality of different messages at ultra highfrequencies.

5 It is well known in connection with transmission over long distancesat ultra high frequencies to provide relay repeater stations which areadapted to receive messages from one station and to repeat these to afurther station. Such known systems employ different communicationchannels in such a manner that either each carrier frequency ismodulated with one message frequency, or that one single carrierfrequency is modulated with several message frequencies by the agency ofintermediate carrier frequencies. The invention deals with the lastmentioned arrangements, although not limited to systems employing relayrepeater stations, but is applicable to all arrangements operatingwithout such stations for interconnecting any two devices.

The invention has for its object to secure reliable operation of thistype of systems by using possibly simple means. The average frequencyrange utilized in interconnections of the aforesaid type involvescertain difficulties, which can be removed merely by long waveoperation. However, the inventive idea proposes a quite differentsolution for obviating occurring dfculties,

According to the present invention, the ultrahigh carrier frequency isdirectly modulated with narrow-band message frequencies, e. g. telegraphsignals, while being indirectly modulated with wide-band messagefrequencies, particularly the speech frequency band, by the agency of anin- 35 termediate carrier frequency which is subsequently suppressed.Preferably only one side band, viz. vthe lower side band of the speechfrequency is transmitted. This side band is located beyond the telegraphfrequencies in the frequency spectrum.

This new arrangement involves following advantages over the abovementioned known systems, which employ one separate carrier for themodulation of each of the different communication channels. It would bedesirable to suppress the intermediate carrier in order to reduce thewidth of the frequency band and to modulate the ultra-high carrierfrequency with one of the side bands obtained due to the intermediatefrequency 5 modulation, however, the suppression of the intermediatefrequency carrier involves considerable difficulties in cases thattone-frequency telegraph channels are concerned, because there are noreliable means available for such suppression within thisfrequencyrange. On the other hand,

(Cl. Z50-9) it must be borne in mind that the expenditure must be keptas low as possible on account of the fact that rather the simplicity ofthe design with respect to the individual stations emphasizes thesuperiority of the ultra short wave operation. 5 According to theinvention, therefore, the carrier is directly modulated with thetelegraph signals, while the messages which demand wider frequency bandsare adapted to modulate an intermediate carrier frequency which issuppressed in any known manner, for instance, in a bridge circuitcomprising dry rectiers in which the modulation is effected. Theultra-high carrier frequency is then modulated with one side band only,preferably the lower. The provision of an intermediate carrier at thereceiving side is then necessary in order to modulate the ultra highfrequency carrier. Difficulties involved with respect to the telegraphchannels are not set up in this case, since the adding of the carrier incases that speech frequency band is concerned, for example, does notrequire such an accuracy. In other words, some allowance is permissiblewithout introducing troubles to the transmission.

The attached drawing in which, Fig. 1 diagrammatically illustrates themodulation frequency band arrangement, and Fig. 2 illustrates a circuitarrangement in block diagram, schematically demonstrates the position ofthe different frequencies within the frequency spectrum. The ultra highcarrier frequency is designated fu generated in transmitter l, while ftI, ft 2 and ft 3 indicate three telegraph channels from telegraphapparatus 2, 3 and 4, and fs the speech channel output from filter 5,the lower side band of which is transmitted only. The not transmittedintermediate carrier frequency of the speech channel is labelled fe. Thebroad band or speech signals fs are generated at 6, and are used tomodulate the carrier frequency fz produced in generator 1, in modulatorThe modulated intermediate carrier is then passed through suppressor 9which suppresses the carrier frequency and a single side band isimpressed on transmitter l through the single rside band lter 5.

What is claimed is:

1. An arrangement for simultaneously transmitting a plurality ofmessages at ultra high frequencies, comprising means for generating anultra high carrier frequency, means for producing a plurality of closelyadjacentnarrow frequency band message wave trains for transmittingseparate messages, said narrow frequency bands all being below a givenfrequency, means 55 quency, and means for modulating said ultra highcarrier frequency with the side band frequency of said modulatedintermediate carrier.

2. An arrangement according to claim 1 fur--l ther comprising means forsuppressing one of the side bands of said Wide frequency band Wave trainwhereby only one side band is used to modulate said ultra high carrierfrequency.

ALFRED'WIESSNER.

